At the risk of getting myself a rain of downvotes here:

An ambulance is an expensive and somewhat rare mini-ER on wheels that's designed to help a small team of expensive and somewhat rare specialists stabilize a dangerous condition on a patient until it reaches a hospital. Since it is important to keep those somewhat rare vehicles and teams in reserve for when they are suddenly urgently needed, you really shouldn't use one as a taxi to the hospital if whatever your condition is doesn't call for that.

(Asking enormous sums of money of the patient for the privilege is IMHO still wrong. The decision to use an ambulance or not should not be based on whether you can can easily part with a couple thousand dollars.)